The use of a cast in the treatment of broken bones has a long history of effectiveness. Traditionally, a layer of cotton cloth is wrapped around the injured limb prior to the application of the plaster or fiberglass cast mixture, in order to keep the skin dry and to create a barrier between the injured person's skin and the cast material. While cotton cloth serves as an adequate barrier, it is known to be water absorbent and difficult to dry when covered with the cast material. A wet cast liner can result in the growth of mold, mildew, and in serious cases, can lead to potentially life-threatening skin infections. Thus, using a cast for fracture treatment requires the injured person to keep the cast as dry as possible, which means cumbersome bathing procedures, and an abstention from any watersport that might result in the immersion of the cast.
Products on the market that provide water resistant or waterproof padding performance include DELTA DRY, PROCEL, ORTHOSKIN, and AQUACAST. However, the construction of these products is such that they do not stretch in the same proportions as a non-waterproof cotton knit material. When applied, the products tend to bunch and wrinkle as they are wrapped around an injured limb, as the average human limb is variable in diameter. This is a reason why orthopedic cast technicians are hesitant to use water resistant materials.
FIG. 1 is a cross section of the prior art padding 50. The prior art padding 50 is comprised of an inner foam 51 covered by outer layers of film 52, 53. The foam 51 and film 52, 53 are both hydrophobic. Adhesives such as the top adhesive layer 54 and bottom adhesive layer 55 are present. Prior art padding also used an adhesive (to help the padding stick to itself when being applied) on one side.
What is needed is a waterproof composite material that allows for stretch in the padding layer.